The present invention relates to a union for butting two plastic bottles reused as a teaching aid, and more particularly to a union for butting two plastic bottles, so that experiments can be conducted in the bottles to simulate the forming of different types of springs and convections due to pressure difference between two spaces.
Plastic bottles are frequently utilized as a teaching aid to simulate the forming a tornado. To do this, two plastic bottles 4 are connected to each other at their mouths by means of a union 3, as shown in FIG. 7. As shown, the union 3 is substantially a tubular member having an annular stop 31 radially inward projected from a middle point of an inner wall surface of the union 3. An annular partition 32 having a central hole 33 is provided at a middle portion of the annular stop 31. The union 3 is provided on its inner wall surface at two sides of the annular stop 31 with two internal screw threads 34, each of which is adapted to engage with an external screw thread 41 around the mouth of the plastic bottle 4, so that two plastic bottles 4 can be separately screwed to two ends of the union 3.
FIG. 8 shows two plastic bottles 4 are connected at their mouths to two ends of the union 3. One of the plastic bottles 4 is partially filled with liquid before being screwed into one end of the union 3. The union 3 with the two plastic bottles 4 is then turned upside down for the bottle 4 having liquid therein to locate at an upper position. When the union 3 and the two connected bottles 4 are properly rotated at the same time, the liquid in the upper bottle 4 flows down into the lower bottle 4 in the form of a whirlpool. One can observe the liquid flow in this experiment to simulate a tornado or a storm. With the union 3, the used plastic bottles 4 could be reused as a good teaching aid and as a good example of environment protection.
However, it is desirable the used plastic bottles could be reused to conduct more experiments in teaching, for example, experiments simulating the forming of different types of springs and convections due to a pressure difference in two spaces.
A primary object of the present invention is to provide a union for butting two plastic bottles reused as a teaching aid, so as to conduct in the plastic bottles experiments simulating the forming of spring and convection due to a pressure difference between two spaces.
Another object of the present invention is to provide a union for butting two plastic bottles reused as a teaching aid, so as to conduct in the plastic bottles experiments simulating the forming of spring and convection at different rates.
To achieve the above and other objects, the union of the present invention mainly includes a hollow tubular body having a radially inward projected middle partition. An internal screw thread is provided on an inner wall surface of the union at each side of the middle partition to engage with an external screw thread on the mouth of the plastic bottle. The middle partition is provided with two symmetrical through holes, each of which is axially divided into two parts by a radially inward projected annular rib. Each part of the through holes is sized for a suction tube of predetermined dimensions to insert thereinto. By separately inserting two or three suction tubes into different parts of the two through holes, screwing the plastic bottles, one of which is partially filled with liquid, to two ends of the union, and turning the union upside down to locate the bottle having liquid at an upper position, different types of springs and convections due to a pressure difference between two spaces could be simulated in the bottles.